Mounting piezoelectric elements



May 26, 1942. P. D. GERBER MOUNTING PIEZOELECTRIC ELEMENTS Filed Dec. 29, 1939 omeg corporates a dust trap.

Patented May 26,1942

2,584,088 MOUNTING rm'zonwcrarc ELEMENTS Paul D. Gerber, 'Woodlynne, N. 1., assignor to Radio Corporation oil America, a corporation of Delaware Application December 29, 21939, Serial No. 311,615

8 Claims. (cam-s21) g ment upon an electrode provided with a-multi- This invention relates to the art of mounting piece-electric crystal elements.

Piano-electric crystals are extremely sensitive to any'iorce' tending to damp their oscillations.

Among the factors inhibiting optimum performance are:,-(a) clamping pressure, (b) friction, (c) adhesion, and (d) the accumulation adjacent the crystal of air borne dust or -of minute crystalline or metal particles generated during the normal operation of the crystal by its movement on its supporting surface.

While clamping pressure can be eliminated (at least in stationary units) by mounting the crystal in an air-gap holder the heretofore proposed solutions of the other problems either give rise to other equally serious problems or are not entirely practical. By way of example; in order to reduce friction between. the crystal and its supporting surface, it'has heretofore been proposed to render both surfaces optically flat, but this has been found to augment the tendency ofthe crystal to resist starting because of the likelihood or adhesion between such highly .finished surfaces.

Accordingly, an object of the present invention is to provide an improved mount for a piezo-electric crystal wherein the tendency .of-the crystal to resist starting due to adhesion is minimized and wherein friction between the crystal and its Another object of the invention is to provide a v simple inexpensive and trouble-free method vand apparatus for mounting a piezo-electrlc element.

In the drawing wherein like reference characters designate the same or corresponding parts in all figures, 1

which inplicity of discrete supports or risers thereon.

The surfaces of the risers preferably comprise fiat areas or lands defining a common plane and the spaces or grooves between these spaced supports comprise relief air channels which prevent adhesion and also constitute an eflective dust trap into which particles tending to accumulate adjacent the supported face at the crystal will fall. i M

The electrode E of Figs. 1 and 2 comprises a base B having a multiplicity of risers R thereon which terminate in flat surfaces S which constitute a gri d-like support for the piezo-electric Figure 2 is an enlarged fragmentary side elevationalviewof the electrode of Fig. l with a crystal supportedthereon,

Figure 3 is an enlarged fragmentary view in 1 perspective n! another electrode embodying the The foregoing and other objects and advantages are achieved in accordance with the invention by mounting'andvibrating a piezo-electric elesimply laid without clamping pressure on crystal to'be supported thereon. As shown, the

risers B. may be in the form oi oblongs whichextend across the plate, but they maybe of substantially any other shape or pattern. By way of .ex-

squares S.

dicated at s, s' in Figs. 2 and 3, respectively, to eliminate any feathers" or other irregularities A which 'ght tend to scratch the surface-of The electrode may be con veniently formed by stamping a flat metal plate P 118118 c stal.

with a tool having a die face of the pattern tie-- sired, after whichthe supporting surface is pre'ferably polished as with felt. I

,The exact depth and pitch of the risers is not its highly polished face to adhere to the supporting surfaces of the risers. The spaces between the risers, however, should be deep enough and wide enough to hold the dust or foreign particles "which'may fall therein when the crystal element is vibrated thereabove. The advantages of an electrode incorporating a. dust it is practically impossible by any washing proc-' ass to entirely rid the crystal or the minute particles of abrasive which become embedded therein during. the grinding operation, Electrodes having apattem similar to that of the one shown in Figs. 1 and Z'gave satisfactory performance when the dimensions of the risers were as.

follows: width .05", spacing .l.", depth .005 to .001". a

lF'ig. 4 shows sf simple air-gap holder wh'ere v in the base E of thehousing H comprises the.

electrode of Figs. 1a and 2. The crystal Q-is in its plane of support.

.as illustrative and not in a limiting sense except as required by the prior art and by the spirit of the appended claims. What is claimed is:

1. Method of mounting a piezoelectric crystal which comprises conductively supporting said crystal without clamping pressure at a multiplicity of discrete .areas about an electrode face thereof.

'2. Method of mounting a piezoelectric crystal which comprises conductively supporting said crystal without clamping pressure upon a multiplicity of discrete surfaces.

3. Method of cperating a piezoelectric crystal having a flat face, which comprises freely supporting said face of said crystal upon a mult plicity of flat raised conductive surfaces having air channels therebetween, whereby adhesion between said flat crystal face and said multiplicity I of flat supporting surfaces is prevented.

4. In combination, an electrode comprising a multiplicity of discrete conductive surfaces defining a plane supporting surface for a piezc-.

electric element and a second electrode mounted above said first-mentioned electrode out of pressure transfer relation with said piezoelectric element.

5. In combination; an electrode comprising a base portion and'a multiplicity of spaced crystalsuppcrting metal risers thereon which terminate inv a common plane, and a second electrode mounted above the plane of said first-mentioned electrode out of contact with said crystal.

6. In combination, an electrode comprising a base portion and a multiplicity of spaced crystal- .supporting risers thereon comprising beveled metal surfaces terminating in a common plane, and a second electrode mounted above said common plane out of contact with said crystal.

7. An electrode of the character described comprising a conductive base having a multiplicity of parallelly arranged conductive lands and grooves thereon.

8. The invention as set forth in claim 7 and v wherein said multiplicity of conductive lands piezoelectric element.

comprise a punctiform-supporting surface for a PAUL D. GERBE 

